JPS6041680Y2 - discharge lamp dimmer - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a discharge lamp dimmer.

Conventionally, a thyristor (for example, S
CR) is used for phase control.

However, according to this, the AC power is turned on and off once every half wave of the AC power, so if the thyristor pause period is extended to reduce the light, the light will tend to flicker, and once it turns off, it will turn off. If this happens, a high voltage will be generated when the lamp is re-ignited, which may have an adverse effect on the life of the discharge lamp.

The purpose of this invention is to eliminate the flickering of the discharge lamp and the reduction in the life of the discharge lamp and to enable dimming.

This idea uses an inverter to light the discharge lamp at a high frequency, and also uses an unstable circuit that can adjust the oscillation cycle, and uses this oscillation output to change the intermittent cycle of the supply input to the inverter. It is made to emit light.

An embodiment of this invention will be described with reference to the drawings.

Reference numeral 1 denotes a power supply terminal to which AC power or DC power is applied.

2 is a full-wave rectifier; when an AC power source is connected to power supply terminal 1, a full-wave rectified DC power source is output from this device, and when a DC power source is connected, the DC current is is output as is.

3 is a diode for backflow prevention, 4 is a smoothing capacitor,
Reference numeral 5 denotes an astable circuit, 6 a transistor that is turned on and off by the oscillation output of the astable circuit 5, and 7 a switching element (for example, a transistor) that is turned on and off as the transistor 6 turns off and on.

8 is an inverter, and 9 is a discharge lamp.

The astable circuit 5 includes a pair of transistors 11.12, a capacitor 13.14 connected between the collector of one transistor and the base of the other transistor, and a collector of each transistor connected via the capacitor. It is composed of a resistor 15, a variable resistor 16, and collector resistors 17 and 18 of each transistor.

The on and off periods of each transistor are controlled by a resistor 15.
16 and capacitors 13 and 14.

This will be described later.

When the transistor 12 is on (off), the transistor 6 is turned off (on), and thereby the switch element 7 is turned on (off).

Therefore, the switch element 7 is turned on and off according to the oscillation period of the astable circuit 5.

It is also assumed that the oscillation period of the astable circuit is set to be sufficiently shorter than the half-wave period of the AC power supply.

In the above configuration, when an AC power source is connected to the power supply terminal 1, the rectified DC current from the full-wave rectifier 2 tends to flow through the switch element 7 to the inverter 8.

If the switch element 7 is repeatedly turned on and off due to the oscillation of the astable circuit 5, the rectified DC current is supplied to the inverter 8 during the on period.

The waveform in FIG. 3 shows this state.

The inverter 8 operates only during the period when the rectified DC current is supplied, and generates a high frequency wave, and the discharge lamp 9 is lit by the high frequency output.

If the off-period of the transistor 12 of the astable circuit 5 is made longer as shown in FIG. The high frequency output from the inverter 8 decreases, and the discharge lamp 8 begins to dim.

That is, by changing the duty of the output pulse of the astable circuit 5, dimming becomes possible.

In this configuration, the switch element 7 is repeatedly turned on and off during each half-wave period of the rectified direct current, so that the discharge lamp does not flicker even when the light is dimmed, as in the case of using a thyristor. Moreover, since the maximum peak value is almost maintained, the lighting of the discharge lamp can be sustained sufficiently.

By the way, in a normal non-stable circuit, it is known that in order to change the on or off period of a pair of transistors, it is sufficient to make the resistance connected to the bases of the transistors variable.

However, in such a normal unstable circuit, for example, in order to lengthen the off period of a subsequent transistor (transistor 12 in the example shown), the resistance value of the resistor connected to the base of that transistor must be changed. Even if it is sufficient to increase the resistance, the resistance must be varied within as large a range as possible in order to prevent this transistor from turning on, that is, to ensure that the unstable circuit stops oscillating.

In practice, this is difficult to achieve, so it is necessary to take measures such as connecting a switch in series with this resistor to separate this resistor from the base of the transistor.

However, this makes the configuration complicated and the operation complicated.

For this reason, in this invention, the variable resistor 16 is connected to the non-stabilizing circuit 5.
The contact 21 is connected to the base of the transistor 12 in the case of FIG.

Note that 22 is a protective resistor for protecting the transistor 12 from being destroyed due to a short circuit between the base and emitter of the transistor 12 when the contactor 21 is moved to the uppermost end, as will be described later.

16a and 16b are resistances of the variable resistor 16 above and below the contactor 21.

Assuming that the transistor 11 is now on and the transistor 12 is off, the capacitor 13 is charged by the current flowing through the resistor 16a1, the protective resistor 22, the capacitor 13, and the transistor 11.

The charging time constant at this time is the capacitor 13 and the resistor 16.
a, 22.

Therefore, by moving the contactor 21 and changing the resistance value of the resistor 16a, the period during which the transistor 11 is on and the transistor 12 is off can be arbitrarily changed.

If the contactor 21 is moved downward and the resistance value of the resistor 16a is increased, the above-mentioned period will gradually become longer, but from the above explanation, when the contactor 21 is moved to the lowest end, For example, the period mentioned above should be the maximum.

However, at this time, the base and emitter of the transistor 12 are short-circuited, so in this state, the transistor 12 can no longer be turned on, and the off state of the transformer 12 is caused by the resistor 16a, and thus This is maintained regardless of the resistance value of the variable resistor 16.

If the transistor 12 is off, the switch element 7 is off, so no current flows through the inverter 8, and the discharge lamp 9 is not lit.

By arbitrarily adjusting the position of the contactor 21 in this manner, it becomes possible to dim the discharge lamp 9 to any desired range from the off state.

FIG. 1 shows an example in which the resistor 16 for charging the capacitor 13 is a variable resistor, while FIG. 2 shows an example in which the resistor for charging the capacitor 14 is a variable resistor 15.

In this case, transistor 11 is off, transistor 1
2 is in the on state, capacitor 14 connects resistor 15
, contact 21, protective resistor 22, capacitor 14,
It is charged by the current flowing through transistor 12.

When the contact 21 is moved to the lowest end, the base and emitter of the transistor 11 are short-circuited and can now be turned on, while the transistor 12 continues to be on.

When the transistor 12 is on, current is supplied to the inverter 8. Therefore, in the configuration of FIG. 2, by arbitrarily adjusting the position of the contactor 21, the discharge lamp 9
It becomes possible to dim the light to any desired range from its maximum lighting state.

As detailed above, according to this invention, the discharge lamp can be dimmed within any range, and no flickering occurs during dimming, and the oscillation period of the unstable circuit can be adjusted to half a wave of the AC power supply. Since it is made sufficiently shorter than the period, the turn-off time of the discharge lamp can be shortened, and therefore, there is an effect that the adverse effect on the life of the discharge lamp due to the high voltage at the time of restriking can be sufficiently avoided.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of this invention, FIG. 2 is a circuit diagram showing another embodiment, and FIGS. 3 and 4 are waveform diagrams for explaining the operation. 2...Full wave rectifier, 5...Unstable circuit, 8...Inverter, 9...Discharge lamp, 15, 16...・Resistance for determining time constant.

Claims (1)

[Scope of utility model registration request] an inverter, a discharge lamp lit by the high frequency output from the inverter, a switch element connected between the inverter and its power source, and a switch element connected between the inverter and the power source, the discharge lamp being lit by the high frequency output from the inverter; an astable circuit that oscillates periodically and controls the switching element to be turned on and off by the oscillation output to intermittently input to the inverter, and a variable resistor connected between the operating power supply terminals of the astable circuit; A discharge lamp dimmer that serves as a resistor for determining the time constant of the astable circuit.